POS1006 DIAGNOSIS OF AXIAL SpA AND ADDITIONAL FEATURES IN HLA-B27 POSITIVE INDIVIDUALS REPORTING CHRONIC INFLAMMATORY BACK PAIN: DATA FROM A LARGE DUTCH POPULATION-BASED COHORT
Authors: S. Kieskamp, S. Arends, E. Brouwer, H. Bootsma, I. M. Nolte, A. Spoorenberg
Journal: Annals of the Rheumatic Diseases (2022)

Background Chronic low back pain (CLBP; back pain &gt;3 months with age of onset &lt;45) and inflammatory back pain (IBP) are regarded as early and key features of axSpA. HLA-B27 is the most important genetic risk factor. Despite improved diagnostics, especially the use of MRI in demonstrating active sacroiliitis, the substantial delay in axSpA diagnosis has not improved 1 . Objectives To explore the presence of CLBP and IBP in combination with HLA-B27 and the presence of other axSpA associated features in the general population. Methods Participants of the Lifelines cohort, a large population-based cohort which is representative of the mostly Caucasian Northern region of the Netherlands 2 , responded to a survey with questions concerning the presence of CLBP and the European Spondyloarthropathy Study Group (ESSG) criteria for IBP. HLA-B haplotypes were imputed from genome-wide SNPs genotyped with the Illumina GSA beadchip-24 v1.0, using the R-package HIBAG with published parameter estimates. Analyses were performed on participants with available HLA-B haplotype and CLBP/IBP data. Prevalence rates were calculated and logistic regression was performed to identify whether participant characteristics and other available SpA features were independently associated with the presence of the key axSpA features HLA-B27, CLBP and IBP. Results 20,619 participants had data available on CLBP, IBP and HLA-B haplotype. Of these participants, 1,610 (7.8%) were HLA-B27+, 3,717 (18.0%) reported CLBP, 2,670 (13.0%) fulfilled the IBP criteria, and 47 (0.23%) reported a previous SpA diagnosis, of which 37 (0.18%) reported axSpA. In total, 226 (1.1%) participants had the combination of CLBP/IBP/HLA-B27. Only 11 (4.9%) of these 226 participants reported a previous SpA diagnosis, all of which were axSpA. Participant characteristics and the presence of other available SpA related features are presented in Table 1. Table 1. Characteristics and features associated with SpA in the different subgroups of Lifelines participants. Data presented as mean ± SD or n (%). 1 Participants already reporting a previous SpA diagnosis excluded from this group. Available data in Lifelines of CLBP/IBP &amp; HLA-B (n=20,619 ) Self-reported SpA diagnosis (n=47 ) CLBP + (n=3,698 1 ) CLBP + /IBP + (n=2,653 1 ) HLA-B27 + (n=1,585 1 ) CLBP + /IBP + / HLA-B27 + (n=226 1 ) General characteristics Male 8173 (39.6%) 24 (51.1%) 1443 (39.0%) 1058 (39.9%) 630 (39.7%) 89 (41.4%) Age 44.2 ± 14.2 48.1 ± 12.6 42.5 ± 13.2 44.0 ± 12.8 44.1 ± 14.1 41.7 ± 12.5 BMI 25.7 ± 4.1 26.7 ± 4.3 26.2 ± 4.5 26.3 ± 4.3 25.7 ± 4.4 25.9 ± 4.6 Features associated with SpA Reported diagnosis of: - Uveitis 11 (0.1%) 1 (2.1%) 1 (0.0%) 0 (0%) 2 (0.1%) 0 (0%) - IBD 179 (0.9%) 3 (6.4%) 31 (0.8%) 22 (0.8%) 14 (0.9%) 2 (0.9%) - Psoriasis 588 (2.9%) 8 (17%) 491 (2.8%) 79 (3.0%) 52 (3.3%) 7 (3.3%) Current NSAID use 766 (3.7%) 20 (42.6%) 252 (6.8%) 189 (7.1%) 82 (5.2%) 22 (10.2%) History of peripheral arthritis 609 (3.0%) 7 (14.9%) 229 (6.2%) 196 (7.4%) 43 (2.7%) 17 (7.9%) Reported rheumatism in FDR 3572 (17.3%) 12 (25.5%) 724 (19.6%) 535 (20.2%) 315 (19.9%) 47 (21.9%) At least 1 of above features 4803 (23.3%) 30 (63.8%) 1013 (27.4%) 744 (28.0%) 418 (26.4%) 69 (32.1%) At least 2 of above features 302 (1.5%) 7 (14.9%) 85 (2.2%) 66 (2.5%) 34 (2.1%) 7 (3.3%) In multivariable logistic regression analysis, current NSAID use and a reported history of peripheral arthritis were independently associated with the axSpA key features CLBP, IBP, and IBP+HLA-B27. Conclusion In this large Dutch population-based cohort only 4,9% of participants presenting the combined axSpA key features IBP and HLA-B27 reported a previous axSpA diagnosis, indicating possible axSpA underdiagnosis. Although not all SpA features were available in Lifelines, current NSAID use and a history of peripheral arthritis in combination with the axSpA key features may have additional value in identifying patients with axSpA in primary care. References [1]Zhao SS et al. Rheumatology (Oxford). 2021;6:60(4):1620-8. [2]Scholtens S et al. Int J Epidemiol. 2015;44:1172-80. Acknowledgements This study was supported by a grant from ReumaNederland. Disclosure of Interests Stan Kieskamp: None declared, Suzanne Arends: None declared, Elisabeth Brouwer Speakers bureau: Roche, Consultant of: Roche, Hendrika Bootsma Speakers bureau: Bristol-Myers Squibb, Novartis, Consultant of: Bristol-Myers Squibb, Roche, Novartis, Medimmune, Union Chimique Belge, Grant/research support from: Unrestricted grants from Briostol-Myers Squibb and Roche, Ilja M. Nolte: None declared, Anneke Spoorenberg Paid instructor for: AbbVie, Consultant of: AbbVie, Novartis Pharma, Pfizer, UCB Pharma, Lilly, Grant/research support from: Novartis Pharma, Pfizer